RAPPORTS. XIV: MASTERMAN — 6 — 



diem, as compared with 30 kilos, per diem in A 3 . There are other indications that the 

 area B 4 is of mixed nature, partaking, partly of the characters of an inshore area and 

 partly of an offshore area. The remaining curves of the same general nature. They 

 show a mid-winter maximum and a minimum in early summer (May, June or July). 

 B 2 and B, give a very slight indication of the spring minimum (April and May) but the 

 autumn minimum shows no trace. The B areas (B 2 , B 3 ) vary from 6 kilos, per diem, 

 (minimum) to 15 — 18 kilos, (maximum), whereas the C areas (d and C 2 ) vary from a 

 minimum of 5 to 2 kilos to a maximum of 11 to 14 kilos. C 3 shows the same character 

 but the average catch is rather higher and in the winter maximum it may exceed the 

 contiguous B areas of B 2 and B 3 . 



In B 5 the catches are very low but otherwise do not differ materially from the 

 neighbouring area B 4 . 



There seem to be clear indications of important seasonal movements. It is evident 

 that there is a migration of soles into the inshore waters during the months of April, 

 May and June, most pronounced on the English coast but also marked in Danish waters. 

 During these months the fish are getting fewer and fewer in numbers in the offshore C 

 areas and the inference can at least be suggested that they move from these areas 

 inshore in a regular migration, which is probably a "spawning migration". After this 

 migration has reached its maximum in May or June, the reverse movement probably sets 

 in producing a gradual decrease in the density of fish in the inshore waters — in other 

 words, the fish probably move into deeper waters during late summer and autumn. 



This general movement is largely masked by the spring and autumn offshore move- 

 ments of soles in the inshore waters. It may be that these movements are chiefly confined 

 to the young or immature soles and a considerable degree of parallelism is to be seen 

 to the well-known inshore migrations of the young plaice. 



The chief features of this rhythmic offshore movement in the sole are these: — 



1. On the Eastern side of the North Sea (A 3 , B 4 ) the migratory movement is less 

 pronounced than on the Western (A^. 



2. On the Eastern side the minimum numbers are in April and September, on the 

 Western they are in March and September. 



3. On the Eastern side the Spring migration is the more marked of the two whilst 

 the reverse is the case in the Western side. 



4. The movement is the most marked in the inshore areas (A) and leaves little or 

 no indication in the offshore (C) areas. 



Plaice. In the case of plaice, it has been possible not only to give the general curves for 



total catch but to dissect them into their constituents for the trade-categories of large, 

 medium and small. Figs. 2 and 3 give diagrams of the curves for each of the important 

 areas and App. Tables 4—7 give the figures on which these diagrams are based. 

 It will be seen that the general character of plaice-distribution, namely, the average size 

 increasing with the distance from shore is applicable not only to the average for the year 

 but for each month of the year. In the inshore areas like A,, B 4 and B 3 the quantities 

 of "small" are greatest and "large" least; though in the two former the quantity of 

 "small" falls to so low a level in midwinter that it is in some cases less than that of 

 large and medium. In general, however, the "small" in these areas is so abundant that 

 it gives its character to the total curve. 



